# leetcode submit region begin(Prohibit modification and deletion)
class Solution(object):
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n == 1:
            return 1

        if n == 2:
            return 2
        dp = {}
        dp[1] = 1
        dp[2] = 2
        for i in range(3, n + 1):
            dp[i] = dp[i - 1] + dp[i - 2]

        return dp[n]

    # leetcode submit region end(Prohibit modification and deletion)


Solution().climbStairs(4)
